The zHome project, a 10-unit townhouse development in Issaquah, Washington, is designed to achieve net-zero energy, among other Living Building Challenge imperatives.

LBC creator Jason McLennan.

LBC Ambassadors-in-training at a Portland, Oregon, workshop.

A composting toilet, 10,000-gallon rainwater storage cistern, and graywater recycling help the Eco-Sense house in Victoria, British Columbia, meet its Water petal imperatives.

With few native building materials to choose from, the distance radius and density threshold limits for red-list compliant materials posed a challenge for the Hawaii Preparatory Academy’s Energy Lab. Project managers had to exercise their ingenuity and creativity to meet the Materials petal imperatives.

Careful material selection, reuse, and restoration were part of this home’s path to earning its LBC petals. (shown before)

Careful material selection, reuse, and restoration were part of this home’s path to earning its LBC petals. (shown after)

Intermediate

The Urban Agriculture imperative encourages self-sufficiency by declaring minimum percentages of the site area to be set aside for “opportunities for agriculture,” which could mean gardens, crops, orchards, or animal husbandry. The percentage of land that needs to be devoted to this imperative varies depending on the project’s density. That is, a country house on 5 acres must devote a higher percentage of land to agriculture compared to an urban home on a tiny city lot.

There are exceptions. These last two imperatives are optional for renovation projects, since the owners can’t change the characteristics of the original site. And projects in rural agricultural areas don’t have to meet the density requirements for Car-Free Living, since greater density in agricultural areas isn’t necessarily desirable.

Energy Net Producer

Relying only on current solar income.

The Energy petal’s Net-Zero Energy imperative is simple: 100% of a project’s energy must come from renewable, on-site sources. These include PV and solar thermal arrays, geothermal systems, wind turbines, microhydro generators, and hydrogen-powered fuel cells (so long as the fuel is generated by renewable energy). Systems may or may not be grid-tied, and the determination is made on a net-annual basis. What isn’t specified is how to achieve this goal—there are no minimum R-values for insulation or blower-door test requirements, for instance—but the implicit assumption is that projects will complement RE systems with energy-efficient design and construction.

There are a few rules. No nuclear energy is allowed. With very few exceptions, no combustion is allowed either, not even wood heaters, as LBC projects should not contribute to pollution or carbon-dioxide emissions. The Net-Zero Energy imperative, along with several others, does allow for something called “scale-jumping” when cost and/or environmental impact make it smart for a project to take part in a larger system. For example, several households might share a PV array or a water cistern, so long as the project doesn’t move too far away from functioning as its own utility.

Documentation requires a short narrative describing the system, photos of the components, and 12 months of energy bills and meter readings. Though challenging, achieving the Energy petal is not as daunting as the Water and Materials petals. Examples of net-zero energy buildings of all scales already exist, and the increasing popularity of programs like LEED and Passivhaus have raised the building industry’s collective IQ around energy performance. Incentives and leasing programs have put renewable energy within more people’s grasp, and there are few, if any code barriers.

Making & Saving Water

Creating water-independent sites, buildings & communities.

The Water petal’s two imperatives direct projects to declare independence from systems that bring water to the site from afar and carry it away once it’s “used.” The Net-Zero Water imperative states that a project must supply all of its water on-site. Residential projects may rely on wells, and rainwater harvesting systems and cisterns, but no chemical treatment is allowed. Instead, systems must use physical or biological filters and/or UV treatment.

As with Energy, the language is not prescriptive; composting toilets are not mandatory, though many LBC projects choose them. At the Eco-Sense residence, an LBC project near Victoria, British Columbia, the owners originally planned to use groundwater for irrigation and captured rainwater for everything else. In the end, it made more sense to use groundwater for household needs, in part because it didn’t require filters and UV treatment, as rainwater does.

Comments (1)

I like the idea of the "Petal" concept. I am dismayed with the current building materials and methods. They are not sustainable and they do not produce a safe building. Building Codes are very weak in North America.
This movement could bring much needed change to the construction industry. One flaw that pops out to me is that building or renovating a house in a major city is not feasible and therefore detracts from the petal idea. Many cities demand that one must connect to water supply and connect to sewers. Also city lots are too small to allow for many aspects of the petal concept.
I moved to a small village and built a straw bale home but had to connect to water, sewer, and could not erect a wind tower. The lot is narrow and it was too difficult to site the house to take advantage of the sun. We are very happy with our house, utilities are low and we do not make a large foot print. If we had greater resources we could have improved our design lowered our foot print. We are like the majority of people with limited resources and we did the best we could with what we had but the petal concept is beyond our financial ability. It would be great if the petal concept could make room for people like ourselves.